Isolation and Identification of Fungal Species from the Insect Pest Callosobruchus maculatus (F.)

Abstract

Cowpea seed beetle Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) is one of the most common and economically important pests of stored cereal products worldwide. Furthermore, these beetles can act as vectors for several fungal post-harvest diseases. The current research aimed to isolate the fungi associated with adults of C. maculatus (F.) (Coleoptera: Bruchidae); the present study aimed to isolate and identify fungi associated with adult insects and evaluate their potential as biocontrol agents against the cowpea beetle, C. maculatus. In this study, we collected C. maculatus adults from the Babylon local market and five regions (Hilah, Mahaweel, Al-Mashrou’, Al-Haswa and Al-Musayyab) with no history of insecticide exposure. A potato dextrose agar medium was used to isolate the fungi attached to the surfaces of adult beetles. By Morphological and microscopic examination, Molecular identification and Sequencing analysis, Twenty-seven genera of fungi were isolated and identified from adult C. maculatus, including Aspergillus, Penicillium, Candida spp, white mycelium, Curvularia, Cladosporium, Chaetomium, Stachybotrys, Rhizopus, Drechslera, Scopulariopsis, Paecilomyces, Mucor, Geotrichum candidum, Streptomyces, Sarocladium, Beauveria bassiana, Talaromyces varians, Sporothrix flocculasa, Pseudozyma flocculasa, and Isaria fumosorosea. The molecular weights of the PCR products for the fungi isolates ranged from 650-700 bp, and the amplified ITS1-5.8S-ITS4 rDNA region of indigenous entomopathogenic fungal isolates showed a high sequence similarity (99-100%) with B. bassiana and M. anisopliae deposited in the NCBIGenebank. The phylogenetic tree analysis of the ITS region sequences showed a high degree of similarity between the isolates under study, ranging from 96.5-100. However, there were differences in the sequences among clades, indicating genetic variation possibly due to mating or mutations in different environments. Our study suggests that the storage pest, C. maculatus, would be essential in spreading fungal contaminants and consequently increasing mycotoxin contamination in stored cowpeas. Keywords: Callosobruchus maculatus, Isolation, Fungi.